1. Field of the Invention
The present invention relates to an electromagnetically operated device. More precisely, the present invention relates to a multiple coil, multiple armature solenoid.
2. Prior Art and Related Information
A solenoid is generally defined as an electrically energized coil of insulated wire that produces a magnetic field within the coil. In a typical solenoid, the iron core is rod-shaped and the conductor coil is tightly wound around the core. When energized, the magnetized core is attracted to ferromagnetic metals. The magnetic attraction draws the core toward the thing to which it is attracted, hence producing work through such movement. Here, the coil and core move in unison.
In another application, the coil surrounds a moveable iron core that is magnetically pulled to a central position with respect to the coil when the coil is energized by a current passing therethrough. In this case, the magnetic core is commonly known in the art as an armature.
When energized, the coil induces a magnetic force upon the armature, which in turn produces a linear mechanical force. With such a design, a solenoid may either pull or push a load through the field generated by the coil. Hence, solenoids convert electrical power to mechanical power.
Conventional solenoid designs are constrained by numerous parameters. One major constraint is a lack of mechanical output force at the initial armature position, known as the breakaway force. Output force is a function of the distance between the armature's leading face and its corresponding seating surface, known as the stop.
FIG. 1 illustrates this concept. FIG. 1 shows a solenoid comprised of a coil 3, and a moveable armature 2, spaced apart from a stop 1. Distance A defines the stroke of the armature 2 when it is energized. When energized, the leading face 4 of the armature 2 moves in direction B through stroke A until contact with the stop 1.
It has been observed that output force decreases substantially as the armature's stroke distance A increases. Obviously then, this physical constraint amounts to serious performance problems when a long stroke and a high breakaway force are required. Indeed, when a long stroke is necessary, large efficiency losses occur as measured from input of the electrical energy into the coil to the output force from the armature. Therefore, a need presently exists for an efficient solenoid even though the armature must undergo a long stroke and experience a high breakaway force.